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Final endgame.cpp space inflate

Browse source 
No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-02-03 16:08:41 +01:00
parent c32904f0a0
commit 82bf08e4f2
1 changed files with 188 additions and 173 deletions
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191
src/endgame.cpp
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@ -559,6 +559,7 @@ ScaleFactor KQKRPScalingFunction::apply(const Position& pos) {
/// which is mostly copied from Glaurung 1.x, and not very pretty. /// which is mostly copied from Glaurung 1.x, and not very pretty.
ScaleFactor KRPKRScalingFunction::apply(const Position &pos) { ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 1); assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.non_pawn_material(weakerSide) == RookValueMidgame); assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
@ -571,15 +572,17 @@ ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
Square brsq = pos.piece_list(weakerSide, ROOK, 0); Square brsq = pos.piece_list(weakerSide, ROOK, 0);
// Orient the board in such a way that the stronger side is white, and the // Orient the board in such a way that the stronger side is white, and the
// pawn is on the left half of the board: // pawn is on the left half of the board.
if(strongerSide == BLACK) { if (strongerSide == BLACK)
{
wksq = flip_square(wksq); wksq = flip_square(wksq);
wrsq = flip_square(wrsq); wrsq = flip_square(wrsq);
wpsq = flip_square(wpsq); wpsq = flip_square(wpsq);
bksq = flip_square(bksq); bksq = flip_square(bksq);
brsq = flip_square(brsq); brsq = flip_square(brsq);
} }
if(square_file(wpsq) > FILE_D) { if (square_file(wpsq) > FILE_D)
{
wksq = flop_square(wksq); wksq = flop_square(wksq);
wrsq = flop_square(wrsq); wrsq = flop_square(wrsq);
wpsq = flop_square(wpsq); wpsq = flop_square(wpsq);
@ -593,78 +596,78 @@ ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
int tempo = (pos.side_to_move() == strongerSide); int tempo = (pos.side_to_move() == strongerSide);
// If the pawn is not too far advanced and the defending king defends the // If the pawn is not too far advanced and the defending king defends the
// queening square, use the third-rank defence: // queening square, use the third-rank defence.
if(r <= RANK_5 && square_distance(bksq, queeningSq) <= 1 && wksq <= SQ_H5 && if ( r <= RANK_5
(square_rank(brsq) == RANK_6 || (r <= RANK_3 && && square_distance(bksq, queeningSq) <= 1
square_rank(wrsq) != RANK_6))) && wksq <= SQ_H5
&& (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6)))
return ScaleFactor(0); return ScaleFactor(0);
// The defending side saves a draw by checking from behind in case the pawn // The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind. // has advanced to the 6th rank with the king behind.
if(r == RANK_6 && square_distance(bksq, queeningSq) <= 1 && if ( r == RANK_6
square_rank(wksq) + tempo <= RANK_6 && && square_distance(bksq, queeningSq) <= 1
(square_rank(brsq) == RANK_1 || && square_rank(wksq) + tempo <= RANK_6
(!tempo && abs(square_file(brsq) - f) >= 3))) && (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3)))
return ScaleFactor(0); return ScaleFactor(0);
if(r >= RANK_6 && bksq == queeningSq && square_rank(brsq) == RANK_1 && if ( r >= RANK_6
(!tempo || square_distance(wksq, wpsq) >= 2)) && bksq == queeningSq
&& square_rank(brsq) == RANK_1
&& (!tempo || square_distance(wksq, wpsq) >= 2))
return ScaleFactor(0); return ScaleFactor(0);
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7 // White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
// and the black rook is behind the pawn. // and the black rook is behind the pawn.
if(wpsq == SQ_A7 && wrsq == SQ_A8 && (bksq == SQ_H7 || bksq == SQ_G7) && if ( wpsq == SQ_A7
square_file(brsq) == FILE_A && && wrsq == SQ_A8
(square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || && (bksq == SQ_H7 || bksq == SQ_G7)
square_rank(wksq) <= RANK_5)) && square_file(brsq) == FILE_A
&& (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5))
return ScaleFactor(0); return ScaleFactor(0);
// If the defending king blocks the pawn and the attacking king is too far // If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw. // away, it's a draw.
if(r <= RANK_5 && bksq == wpsq + DELTA_N && if ( r <= RANK_5
square_distance(wksq, wpsq) - tempo >= 2 && && bksq == wpsq + DELTA_N
square_distance(wksq, brsq) - tempo >= 2) && square_distance(wksq, wpsq) - tempo >= 2
&& square_distance(wksq, brsq) - tempo >= 2)
return ScaleFactor(0); return ScaleFactor(0);
// Pawn on the 7th rank supported by the rook from behind usually wins if the // Pawn on the 7th rank supported by the rook from behind usually wins if the
// attacking king is closer to the queening square than the defending king, // attacking king is closer to the queening square than the defending king,
// and the defending king cannot gain tempi by threatening the attacking // and the defending king cannot gain tempi by threatening the attacking rook.
// rook. if ( r == RANK_7
if(r == RANK_7 && f != FILE_A && square_file(wrsq) == f && f != FILE_A
&& square_file(wrsq) == f
&& wrsq != queeningSq && wrsq != queeningSq
&& (square_distance(wksq, queeningSq) < && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
square_distance(bksq, queeningSq) - 2 + tempo) && (square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo))
&& (square_distance(wksq, queeningSq) < return ScaleFactor(SCALE_FACTOR_MAX - 2 * square_distance(wksq, queeningSq));
square_distance(bksq, wrsq) + tempo))
return ScaleFactor(SCALE_FACTOR_MAX
- 2 * square_distance(wksq, queeningSq));
// Similar to the above, but with the pawn further back: // Similar to the above, but with the pawn further back
if(f != FILE_A && square_file(wrsq) == f && wrsq < wpsq if ( f != FILE_A
&& (square_distance(wksq, queeningSq) < && square_file(wrsq) == f
square_distance(bksq, queeningSq) - 2 + tempo) && wrsq < wpsq
&& (square_distance(wksq, wpsq + DELTA_N) < && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
square_distance(bksq, wpsq + DELTA_N) - 2 + tempo) && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
&& (square_distance(bksq, wrsq) + tempo >= 3 && ( square_distance(bksq, wrsq) + tempo >= 3
|| (square_distance(wksq, queeningSq) < || ( square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo
square_distance(bksq, wrsq) + tempo && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wrsq) + tempo))))
&& (square_distance(wksq, wpsq + DELTA_N) < return ScaleFactor( SCALE_FACTOR_MAX
square_distance(bksq, wrsq) + tempo)))) - (8 * square_distance(wpsq, queeningSq)
return + 2 * square_distance(wksq, queeningSq)));
ScaleFactor(SCALE_FACTOR_MAX
- (8 * square_distance(wpsq, queeningSq) +
2 * square_distance(wksq, queeningSq)));
// If the pawn is not far advanced, and the defending king is somewhere in // If the pawn is not far advanced, and the defending king is somewhere in
// the pawn's path, it's probably a draw: // the pawn's path, it's probably a draw.
if(r <= RANK_4 && bksq > wpsq) { if (r <= RANK_4 && bksq > wpsq)
if(square_file(bksq) == square_file(wpsq)) {
if (square_file(bksq) == square_file(wpsq))
return ScaleFactor(10); return ScaleFactor(10);
if(abs(square_file(bksq) - square_file(wpsq)) == 1 if ( abs(square_file(bksq) - square_file(wpsq)) == 1
&& square_distance(wksq, bksq) > 2) && square_distance(wksq, bksq) > 2)
return ScaleFactor(24 - 2 * square_distance(wksq, bksq)); return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
} }
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
} }
@ -674,6 +677,7 @@ ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
/// is actively placed, the position is drawish. /// is actively placed, the position is drawish.
ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) { ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame); assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 2); assert(pos.piece_count(strongerSide, PAWN) == 2);
assert(pos.non_pawn_material(weakerSide) == RookValueMidgame); assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
@ -684,23 +688,23 @@ ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) {
Square bksq = pos.king_square(weakerSide); Square bksq = pos.king_square(weakerSide);
// Does the stronger side have a passed pawn? // Does the stronger side have a passed pawn?
if(pos.pawn_is_passed(strongerSide, wpsq1) || if ( pos.pawn_is_passed(strongerSide, wpsq1)
pos.pawn_is_passed(strongerSide, wpsq2)) || pos.pawn_is_passed(strongerSide, wpsq2))
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
Rank r = Max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2)); Rank r = Max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
if(file_distance(bksq, wpsq1) <= 1 && file_distance(bksq, wpsq2) <= 1 if ( file_distance(bksq, wpsq1) <= 1
&& relative_rank(strongerSide, bksq) > r) { && file_distance(bksq, wpsq2) <= 1
switch(r) { && relative_rank(strongerSide, bksq) > r)
{
switch (r) {
case RANK_2: return ScaleFactor(10); case RANK_2: return ScaleFactor(10);
case RANK_3: return ScaleFactor(10); case RANK_3: return ScaleFactor(10);
case RANK_4: return ScaleFactor(15); case RANK_4: return ScaleFactor(15);
case RANK_5: return ScaleFactor(20); case RANK_5: return ScaleFactor(20);
case RANK_6: return ScaleFactor(40); case RANK_6: return ScaleFactor(40);
default: assert(false); default: assert(false);
} }
} }
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
@ -712,6 +716,7 @@ ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) {
/// the same rook file and are blocked by the defending king, it's a draw. /// the same rook file and are blocked by the defending king, it's a draw.
ScaleFactor KPsKScalingFunction::apply(const Position &pos) { ScaleFactor KPsKScalingFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == Value(0)); assert(pos.non_pawn_material(strongerSide) == Value(0));
assert(pos.piece_count(strongerSide, PAWN) >= 2); assert(pos.piece_count(strongerSide, PAWN) >= 2);
assert(pos.non_pawn_material(weakerSide) == Value(0)); assert(pos.non_pawn_material(weakerSide) == Value(0));
@ -720,25 +725,27 @@ ScaleFactor KPsKScalingFunction::apply(const Position &pos) {
Bitboard pawns = pos.pawns(strongerSide); Bitboard pawns = pos.pawns(strongerSide);
// Are all pawns on the 'a' file? // Are all pawns on the 'a' file?
if((pawns & ~FileABB) == EmptyBoardBB) { if ((pawns & ~FileABB) == EmptyBoardBB)
{
// Does the defending king block the pawns? // Does the defending king block the pawns?
Square ksq = pos.king_square(weakerSide); Square ksq = pos.king_square(weakerSide);
if(square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1) if (square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1)
return ScaleFactor(0); return ScaleFactor(0);
else if(square_file(ksq) == FILE_A && else if( square_file(ksq) == FILE_A
(in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB) && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
return ScaleFactor(0); return ScaleFactor(0);
else else
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
} }
// Are all pawns on the 'h' file? // Are all pawns on the 'h' file?
else if((pawns & ~FileHBB) == EmptyBoardBB) { else if ((pawns & ~FileHBB) == EmptyBoardBB)
{
// Does the defending king block the pawns? // Does the defending king block the pawns?
Square ksq = pos.king_square(weakerSide); Square ksq = pos.king_square(weakerSide);
if(square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1) if (square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1)
return ScaleFactor(0); return ScaleFactor(0);
else if(square_file(ksq) == FILE_H && else if ( square_file(ksq) == FILE_H
(in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB) && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
return ScaleFactor(0); return ScaleFactor(0);
else else
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
@ -755,6 +762,7 @@ ScaleFactor KPsKScalingFunction::apply(const Position &pos) {
/// a draw. /// a draw.
ScaleFactor KBPKBScalingFunction::apply(const Position &pos) { ScaleFactor KBPKBScalingFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1); assert(pos.piece_count(strongerSide, BISHOP) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 1); assert(pos.piece_count(strongerSide, PAWN) == 1);
@ -767,16 +775,16 @@ ScaleFactor KBPKBScalingFunction::apply(const Position &pos) {
Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP, 0); Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP, 0);
Square weakerKingSq = pos.king_square(weakerSide); Square weakerKingSq = pos.king_square(weakerSide);
// Case 1: Defending king blocks the pawn, and cannot be driven away. // Case 1: Defending king blocks the pawn, and cannot be driven away
if(square_file(weakerKingSq) == square_file(pawnSq) if ( square_file(weakerKingSq) == square_file(pawnSq)
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
&& (square_color(weakerKingSq) != square_color(strongerBishopSq) && ( square_color(weakerKingSq) != square_color(strongerBishopSq)
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6)) || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
return ScaleFactor(0); return ScaleFactor(0);
// Case 2: Opposite colored bishops. // Case 2: Opposite colored bishops
if(square_color(strongerBishopSq) != square_color(weakerBishopSq)) { if (square_color(strongerBishopSq) != square_color(weakerBishopSq))
{
// We assume that the position is drawn in the following three situations: // We assume that the position is drawn in the following three situations:
// //
// a. The pawn is on rank 5 or further back. // a. The pawn is on rank 5 or further back.
@ -787,14 +795,14 @@ ScaleFactor KBPKBScalingFunction::apply(const Position &pos) {
// These rules are probably not perfect, but in practice they work // These rules are probably not perfect, but in practice they work
// reasonably well. // reasonably well.
if(relative_rank(strongerSide, pawnSq) <= RANK_5) if (relative_rank(strongerSide, pawnSq) <= RANK_5)
return ScaleFactor(0); return ScaleFactor(0);
else { else
Bitboard ray = {
ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S); Bitboard ray = ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S);
if(ray & pos.kings(weakerSide)) if (ray & pos.kings(weakerSide))
return ScaleFactor(0); return ScaleFactor(0);
if((pos.piece_attacks<BISHOP>(weakerBishopSq) & ray) if( (pos.piece_attacks<BISHOP>(weakerBishopSq) & ray)
&& square_distance(weakerBishopSq, pawnSq) >= 3) && square_distance(weakerBishopSq, pawnSq) >= 3)
return ScaleFactor(0); return ScaleFactor(0);
} }
@ -809,6 +817,7 @@ ScaleFactor KBPKBScalingFunction::apply(const Position &pos) {
/// it's a draw. /// it's a draw.
ScaleFactor KBPKNScalingFunction::apply(const Position &pos) { ScaleFactor KBPKNScalingFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame); assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1); assert(pos.piece_count(strongerSide, BISHOP) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 1); assert(pos.piece_count(strongerSide, PAWN) == 1);
@ -820,9 +829,9 @@ ScaleFactor KBPKNScalingFunction::apply(const Position &pos) {
Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0); Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0);
Square weakerKingSq = pos.king_square(weakerSide); Square weakerKingSq = pos.king_square(weakerSide);
if(square_file(weakerKingSq) == square_file(pawnSq) if ( square_file(weakerKingSq) == square_file(pawnSq)
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
&& (square_color(weakerKingSq) != square_color(strongerBishopSq) && ( square_color(weakerKingSq) != square_color(strongerBishopSq)
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6)) || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
return ScaleFactor(0); return ScaleFactor(0);
@ -835,6 +844,7 @@ ScaleFactor KBPKNScalingFunction::apply(const Position &pos) {
/// the pawn from advancing, the position is drawn. /// the pawn from advancing, the position is drawn.
ScaleFactor KNPKScalingFunction::apply(const Position &pos) { ScaleFactor KNPKScalingFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame); assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame);
assert(pos.piece_count(strongerSide, KNIGHT) == 1); assert(pos.piece_count(strongerSide, KNIGHT) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 1); assert(pos.piece_count(strongerSide, PAWN) == 1);
@ -844,12 +854,12 @@ ScaleFactor KNPKScalingFunction::apply(const Position &pos) {
Square pawnSq = pos.piece_list(strongerSide, PAWN, 0); Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
Square weakerKingSq = pos.king_square(weakerSide); Square weakerKingSq = pos.king_square(weakerSide);
if(pawnSq == relative_square(strongerSide, SQ_A7) && if ( pawnSq == relative_square(strongerSide, SQ_A7)
square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1) && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
return ScaleFactor(0); return ScaleFactor(0);
if(pawnSq == relative_square(strongerSide, SQ_H7) && if ( pawnSq == relative_square(strongerSide, SQ_H7)
square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1) && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
return ScaleFactor(0); return ScaleFactor(0);
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
@ -864,6 +874,7 @@ ScaleFactor KNPKScalingFunction::apply(const Position &pos) {
/// (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1). /// (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
ScaleFactor KPKPScalingFunction::apply(const Position &pos) { ScaleFactor KPKPScalingFunction::apply(const Position &pos) {
assert(pos.non_pawn_material(strongerSide) == Value(0)); assert(pos.non_pawn_material(strongerSide) == Value(0));
assert(pos.non_pawn_material(weakerSide) == Value(0)); assert(pos.non_pawn_material(weakerSide) == Value(0));
assert(pos.piece_count(WHITE, PAWN) == 1); assert(pos.piece_count(WHITE, PAWN) == 1);
@ -872,20 +883,23 @@ ScaleFactor KPKPScalingFunction::apply(const Position &pos) {
Square wksq, bksq, wpsq; Square wksq, bksq, wpsq;
Color stm; Color stm;
if(strongerSide == WHITE) { if (strongerSide == WHITE)
{
wksq = pos.king_square(WHITE); wksq = pos.king_square(WHITE);
bksq = pos.king_square(BLACK); bksq = pos.king_square(BLACK);
wpsq = pos.piece_list(WHITE, PAWN, 0); wpsq = pos.piece_list(WHITE, PAWN, 0);
stm = pos.side_to_move(); stm = pos.side_to_move();
} }
else { else
{
wksq = flip_square(pos.king_square(BLACK)); wksq = flip_square(pos.king_square(BLACK));
bksq = flip_square(pos.king_square(WHITE)); bksq = flip_square(pos.king_square(WHITE));
wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0)); wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
stm = opposite_color(pos.side_to_move()); stm = opposite_color(pos.side_to_move());
} }
if(square_file(wpsq) >= FILE_E) { if (square_file(wpsq) >= FILE_E)
{
wksq = flop_square(wksq); wksq = flop_square(wksq);
bksq = flop_square(bksq); bksq = flop_square(bksq);
wpsq = flop_square(wpsq); wpsq = flop_square(wpsq);
@ -893,12 +907,13 @@ ScaleFactor KPKPScalingFunction::apply(const Position &pos) {
// If the pawn has advanced to the fifth rank or further, and is not a // If the pawn has advanced to the fifth rank or further, and is not a
// rook pawn, it's too dangerous to assume that it's at least a draw. // rook pawn, it's too dangerous to assume that it's at least a draw.
if(square_rank(wpsq) >= RANK_5 && square_file(wpsq) != FILE_A) if ( square_rank(wpsq) >= RANK_5
&& square_file(wpsq) != FILE_A)
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a // Probe the KPK bitbase with the weakest side's pawn removed. If it's a
// draw, it's probably at least a draw even with the pawn. // draw, it's probably at least a draw even with the pawn.
if(probe_kpk(wksq, wpsq, bksq, stm)) if (probe_kpk(wksq, wpsq, bksq, stm))
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
else else
return ScaleFactor(0); return ScaleFactor(0);
@ -919,11 +934,11 @@ namespace {
// Probe the KP vs K bitbase: // Probe the KP vs K bitbase:
int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) { int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) {
int wp = int(square_file(wpsq)) + (int(square_rank(wpsq)) - 1) * 4; int wp = int(square_file(wpsq)) + (int(square_rank(wpsq)) - 1) * 4;
int index = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*wp; int index = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*wp;
assert(index >= 0 && index < 24576*8); assert(index >= 0 && index < 24576*8);
return KPKBitbase[index/8] & (1 << (index&7)); return KPKBitbase[index/8] & (1 << (index&7));
} }
} }